Pixel structure of a liquid crystal display and fabricating method with black matrix pattern covering over TFT and directly lying on parts of pixel electrode pattern

ABSTRACT

A method of fabricating a pixel structure of liquid crystal display is described. A transparent conductive layer and a first metal layer are formed over a substrate sequentially. The first metal layer and the transparent conductive layer are patterned to form a gate pattern and a pixel electrode pattern. A gate insulating layer and a semiconductor layer are formed over the substrate sequentially. A patterning process is performed to preserve the semiconductor layer and the gate insulating layer above the gate pattern and remove the first metal layer of the pixel electrode pattern. A second metal layer is formed over the substrate. The second metal layer is patterned to form a source pattern and a drain pattern. A black material layer is formed over the substrate, and then the black material layer is patterned to form a black matrix pattern uncovering the transparent conductive layer of the pixel electrode pattern.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the priority benefit of Taiwan applicationserial no. 93124315, filed on Aug. 13, 2004. All disclosure of theTaiwan application is incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of Invention

The present invention relates to a pixel structure of a liquid crystaldisplay (LCD) and the method for fabricating the pixel, and a LCD panel.More particularly, the present invention relates to a pixel structure ofa liquid crystal display (LCD) and the method for fabricating the pixel,and a LCD panel, using four photomasks to form the black matrix on thethin film transistor (TFT) array.

2. Description of Related Art

The TFT LCD panel mainly includes a TFT-array substrate with a TFTarray, a color-filter substrate with a color filter array, and a liquidcrystal layer between the two substrates, wherein the TFT-arraysubstrate is formed by several pixels, and each pixel includes one TFTand one pixel electrode.

The conventional method to form the pixel structure of the TFT LCD needsfive photomasks. The first photomask is used to define a first metallayer, so as to form a scan line and a gate electrode of the TFT. Thesecond photomask is used to define a channel layer and an ohm contactlayer of the contact layer. The third photomask is used to define asecond metal layer, to form a data line and source/drain electrodes ofthe TFT. The fourth photomask is used to pattern a protection layer. Thefifth photomask is used to pattern a transparent conductive layer, so asto form the pixel electrode.

In addition, the color-filter substrate is implemented with aphotoresist pattern with three colors of red, green, and blue, but alsoimplemented with a black matrix between the color photoresist patterns.The color photoresist patterns on the color filter substrate are withrespect to the pixels on the TFT-array substrate, and the black matrixpattern is with respect to the metal lines on the TFT-array substrate.

However, as the trend for the TFT LCD having been developed toward agreater size in fabrication, it would confront many issues to be solved,such as decrease of yield rate and throughput. In this situation, if thenumber of the photomasks can be reduced, the number of photolithographicprocesses on the film layers can be reduced, and thereby the fabricationtime can be reduced, the throughput can increase, and then thefabrication cost is reduced.

SUMMARY OF THE INVENTION

With an objective, the invention provides a pixel structure of LCD. Thepixel structure can be formed by using four photomasks, and the pixelstructure further includes the formation of black matrix pattern.

With another objective, the invention provides method for forming apixel structure of LCD. The method uses four photomask processes. Thefour photomask processes can also form the black matrix pattern on aTFT-array substrate.

With further another objective, the invention provides an LCD panel. TheTFT-array substrate of the LCD panel includes the implementation ofblack matrix pattern.

The invention provides a method for forming a pixel structure of LCD.The method includes sequentially forming a transparent conductive layerand a first metal layer on a substrate. A first photomask process isperformed, to pattern the first metal layer and the transparentconductive layer, so as to define a gate electrode pattern and a pixelelectrode pattern. Then, a gate insulating layer and a semiconductorlayer are sequentially formed over the substrate, to cover over the gateelectrode pattern and the pixel electrode pattern. A second photomaskprocess is performed to pattern the gate insulating layer and thesemiconductor layer, wherein a portion above the gate electrode remains,and the first metal layer on the pixel electrode is also removed. Then,a second metal layer is formed over the substrate, and a third photomaskprocess is performed to pattern the second metal layer, wherein aremaining portion of the second metal layer on the semiconductor layerforms a source electrode pattern and a drain electrode pattern. Then, ablack matrix material layer is formed over the substrate, and a fourthphotomask process is performed to pattern the black matrix materiallayer, so as to form a black matrix pattern and expose the transparentelectrode layer of the pixel electrode pattern.

The invention further provides a pixel structure of LCD. The pixelstructure includes a TFT, a pixel electrode pattern, and a black matrixpattern. Wherein, the TFT is disposed on a surface of a substrate, andthe TFT includes a gate electrode pattern, a gate insulating layerdisposed on the gate electrode pattern, a semiconductor layer over thegate insulation layer, and a source electrode pattern as well as a drainelectrode pattern formed over the semiconductor layer. The pixelelectrode pattern is disposed on the surface of the substrate, and thepixel electrode pattern electrically contacts with the drain electrodepattern of the TFT. In addition, the black matrix pattern covers the TFTand exposes the foregoing pixel electrode pattern.

The invention further provides an LCD panel, including a TFT-arraysubstrate, a color-filter substrate, and a liquid crystal layer. Whereinthe TFT-array substrate has several pixels, and each of the pixelsincludes a TFT, a pixel electrode pattern, and a black matrix pattern.Wherein, the TFT includes a gate electrode pattern, a gate insulatinglayer disposed on the gate electrode pattern, a semiconductor layercovering over the gate insulating layer, and a source/drain electrodepattern formed on the semiconductor layer. The pixel electrode patternis disposed on the surface of the substrate, and the pixel electrodepattern electrically contacts with the drain electrode pattern of theTFT. Further, the black matrix pattern covers the TFT and exposes thepixel electrode pattern.

The invention can just use four photomask processes to accomplish theformation of pixel structure. Also and, in the four photomask processes,it also includes defining the black matrix pattern on the TFT-arraysubstrate. The method of the invention can reduce the number ofphotomasks being used in the conventional fabrication processes, so thatit has the advantages that the throughput can increase and fabricationcan be reduced.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings are included to provide a furtherunderstanding of the invention, and are incorporated in and constitute apart of this specification. The drawings illustrate embodiments of theinvention and, together with the description, serve to explain theprinciples of the invention.

FIG. 1 is a top view, schematically illustrating a pixel structure ofthe LCD, according to a preferred embodiment of the invention.

FIGS. 2A-2H are cross-sectional views, schematically illustrating thefabrication procedure for the pixel structure of the LCD, according to afirst preferred embodiment of the invention.

FIGS. 3A-3B are cross-sectional views, schematically illustrating thefabrication procedure for the pixel structure of the LCD, according to asecond preferred embodiment of the invention.

FIGS. 4A-4B are cross-sectional views, schematically illustrating thefabrication procedure for the pixel structure of the LCD, according tothe second preferred embodiment of the invention.

FIGS. 5A-5B are cross-sectional views, schematically illustrating thefabrication procedure for the pixel structure of the LCD, according tothe third preferred embodiment of the invention.

FIG. 6 is a cross-sectional view, schematically illustrating an LCD,according to a preferred embodiment of the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Four Photomask Processes

First Embodiment

FIG. 1 is a top view, schematically illustrating a pixel structure ofthe LCD, according to a preferred embodiment of the invention. FIGS.2A-2H are cross-sectional views, schematically illustrating thefabrication procedure for one of the pixel structures of the LCD,according to a first preferred embodiment of the invention.

In FIG. 1 and FIG. 2A, a transparent conductive layer 102 and a firstmetal layer 104 are sequentially formed over a substrate 100. In thepreferred embodiment, the substrate 100 can include, for example, apreset region for forming a TFT T, a preset region for forming a pixelelectrode P, a preset region for forming a storage capacitor C, and apreset region for forming multiple bonding pads B and B′. The substrate100 can be, for example, a glass substrate or a transparent plasticsubstrate. The transparent conductive layer 102 can be, for example,metal oxide, such as indium-tin oxide (ITO), indium-zinc oxide (IZO), orother like material. The first metal layer 104 can be, for example, Cr,W, Ta, Ti, Mo, Al, or alloy thereof. Particularly, if the transparentelectrode layer 102 uses the ITO or IZO, then the first metal layer 104preferably is Cr, W, Ta, Ti, Mo, or alloy thereof.

Then, a first photomask process is performed to form a patternedphotoresist layer 106 on the first metal layer 104. The patternedphotoresist layer 106 is used as the etching mask to perform an etchingprocess, so as to pattern the first metal layer 104 and the transparentconductive layer 102, and then form the patterned first metal layer 104a and the patterned transparent conductive layer 102 a, as shown in FIG.2B. In the preferred embodiment, the first photomask process is todefine a gate electrode pattern 108 at the preset region for forming aTFT T, and a pixel electrode pattern 110 at the preset region forforming a pixel electrode P, and define a scan line 150, as shown inFIG. 1, for electrically coupling with the gate electrode pattern 108.

In another embodiment, it can further include defining the lowerelectrode pattern 112 within the preset region for forming the storagecapacitor C. The storage capacitor C includes, for example, a storagecapacitor on gate (Cs on gate). In another embodiment, the firstphotomask process can further include defining a bonding pad pattern114, which is electrically coupled to the scan line 150, within thepreset region for forming the bonding pad B at an edge of the substrate100. It further includes defining a separate bonding pad pattern 114 a,which is shown in cross-sectional view and is the same as or aboutsimilar to the bonding pad B′, within the preset region for forming thebonding pad B at another edge of the substrate 100. In anotherembodiment, the first photomask process further includes defining thelower electrode pattern 112 and the bonding pad pattern 114.

Referring to FIG. 1 and FIG. 2C, a gate insulating layer 116 and asemiconductor layer 118 are sequentially formed over the substrate 100,to cover the previously formed structure. In a preferred embodiment, thegate insulating layer 116 can be, for example, silicon nitride, siliconoxide, or silicon oxynitride. The semiconductor layer 118 includes, forexample, a channel layer such as amorphous silicon and an ohm contactlayer such as doped amorphous silicon.

Then, a second photomask process is performed to form a patternedphotoresist layer 120 on the semiconductor layer 118, and thephotoresist layer 120 is used as an etching mask to perform an etchingprocess. As shown in FIG. 2D, the semiconductor layer 118 and the gateinsulating layer 116 are patterned to form a patterned semiconductorlayer 118 a and a patterned gate insulating layer 116 a. The first metallayer 114 a on the pixel electrode pattern 110 is also removed, whereinonly the transparent conductive layer 102 a of the pixel electrode 110remains. In another embodiment, for the second photomask process, thesemiconductor layer 118 a and the gate insulating layer 116 a above thegate electrode pattern 108 remain.

In another embodiment, the second photomask process can further allowthe semiconductor layer 118 a and the gate insulating layer 116 a abovethe electrode pattern 112 to remain, for use as the capacitordielectric. In further another embodiment, the second photomask processfurther includes removing a portion of the semiconductor layer 118 a andgate insulating layer 116 a over the bonding pad pattern 114, and aportion of the first metal layer 104 a of the bonding pad pattern 114.As a result, the transparent conductive layer 102 a of the bonding padpattern 114 is exposed. In another embodiment, the second photomaskprocess further includes that the semiconductor layer 118 a and the gateinsulating layer 116 a over the lower electrode pattern 112 and thebonding pad pattern 114 remain, and a portion of the first metal layer104 a of the bonding pad pattern 114 is removed to expose thetransparent conductive layer 102 a of the bonding pad pattern 114.

Referring to FIG. 1 and FIG. 2E, a second metal layer 122 is depositedover the substrate 100, to cover the previously formed structure. In apreferred embodiment, the second metal layer 122 includes, for example,Cr, W, Ta, Ti, Mo, Al, or alloy thereof.

Then, a third photomask process is performed to form a patternedphotoresist layer 124 on the second metal layer 122, and the photoresistlayer 124 is used as the etching mask to perform an etching process. Thesecond metal layer 122 is patterned to form a patterned second metallayer 122 a, as shown in FIG. 2F. In an embodiment, the second metallayer 122 a over the gate electrode pattern 108 is a source electrodepattern 126 and a drain electrode pattern 128, and the drain electrodepattern 128 is electrically connected to the pixel electrode pattern110. Moreover, in the third photomask process, it further defines thesource electrode pattern 126 to be coupled to a data line 160, as shownin FIG. 1. In another embodiment, while patterning the second metallayer 122, it further includes simultaneously reducing a portion ofthickness of the semiconductor layer 118 a between the source electrodepattern 126 and the drain electrode pattern 128, wherein a portion ofthe ohm contact layer is for example removed, and the semiconductorlayer 118 b is formed, so as to form a channel layer 119 between thesource electrode pattern 126/drain electrode pattern 128 and the gateinsulating layer 108.

In another embodiment, the third photomask process further includes thatthe second metal layer 122 a above the corresponding lower electrodepattern 112 remains to serve as an upper electrode 129 of the pixelstorage capacitor. The upper electrode 129 is electrically coupled withthe pixel electrode pattern 110, so that the upper electrode 129, thelower electrode pattern 112 and the dielectric material between the twoelectrodes, such as the gate insulating layer 116 a and thesemiconductor layer 118 a, form a pixel storage capacitor. In anotherembodiment, the third photomask process further includes that the secondmetal layer 122 a over the corresponding bonding pad pattern 114remains, and the second metal layer 122 a is electrically contacted withthe first metal layer 104 a and the transparent conductive layer 102 a.Also and, a second metal layer 122 a is formed within the preset regionfor forming the bonding pad B′ at the edge of the substrate 100, withelectric connection to data line 160, so as to serve as a portion of thebonding pad 114 a. Preferably, the structure of the bonding pad B′ isthe same as or about the same as the structure of the bonding pad B.Further in another embodiment, the third photomask process is furtherincluded, wherein the second metal layer 122 a above the correspondinglower electrode pattern 112 and the bonding pad pattern 114, 114 aremain.

Referring to FIG. 1 and FIG. 2G, a black material layer 202 is depositedover the substrate 100, to cover the previously formed structure. In anembodiment, the black material layer 202 can be, for example, blackorganic material or black inorganic insulating material. The blackorganic material is, for example, black resin. It should be noted thatthe invention is not necessary to limit the material for the blackmaterial layer 202. Any material capable of shielding the light and canbe used to form the black matrix is suitable for use. Preferably, it canalso serve as the protection material layer.

After then, a fourth photomask process is performed to form a patternedphotoresist layer 212 on the black material layer 202, and an etchingprocess is performed by using the photoresist layer 212 as the etchingmask. The black material layer 202 is patterned into black matrixpattern 202 a, as shown in FIG. 2H. In another embodiment, the blackmatrix pattern 202 a exposes the transparent conductive layer 102 a ofthe pixel electrode pattern 110. In another embodiment, the black matrixpattern 202 a further exposes the transparent conductive layer 102 a ofthe bonding pad patterns 114, 114 a, so as allow to be electricallycoupled to the external circuit.

It should be noted that if the foregoing black material layer 202 is aphotosensitive material, then it is not necessary to form the patternedphotoresist layer 212 on the black material layer 202, and the lightexposure and image development procedures can be directly performed onthe black material layer 202 to pattern and form the black matrixpattern 202 a. The black matrix pattern 202 a exposes the transparentconductive layer 102 a of the pixel electrode pattern 110 and thetransparent conductive layer 102 a of the bonding pad patterns 114, 114a, so as allow to be electrically coupled to the external circuit.

Second Embodiment

FIGS. 4A-4B are cross-sectional views, schematically illustrating thefabrication procedure for the pixel structure of the LCD, according tothe second preferred embodiment of the invention. In FIG. 3A, FIG. 3A issubsequent to the fabrication processes in FIGS. 2A-2F. That is, afterthe third photomask process to form the second metal layer, a protectionlayer 200 is formed over the substrate 100, and a black material layer202 is form on the protection layer 200. In an embodiment, theprotection layer 200 includes, for example, silicon oxide, siliconnitride, silicon oxynitride, or organic material. The black materiallayer 202 can be the black organic material or black inorganic materialas previously mentioned, but also can be the metallic material with thecapability of shielding light.

After then, a fourth photomask process is performed to form a patternedphotoresist layer 212 on the black material layer 202, and an etchingprocess is performed by using the photoresist layer 212 as an etchingmask, so as to pattern the black material layer 202 and the protectionlayer 200, and thereby form the black matrix pattern 202 a and theprotection layer 200 a with similar pattern to the black matrix pattern202 a, as shown in FIG. 3B. In an embodiment, the black matrix pattern202 a and the protection layer 200 a expose the transparent conductivelayer 102 a of the pixel electrode pattern 110. In another embodiment,the black matrix pattern 202 a and the protection layer 200 a furtherexpose the transparent conductive layer 102 a of the bonding pads 114,114 a, so as to allow the electric connection to the external circuit.

Likewise, if the black material layer 202 of FIG. 3A uses thephotosensitive material, then it is not necessary to form the patternedphotoresist layer 212 on the black material layer 202, and the lightexposure and image development procedures can be directly performed onthe black material layer 202 to pattern and form the black matrixpattern 202 a. Then, the black matrix pattern 202 a is directly used asthe etching mask to perform the etching process and pattern theprotection layer 200, which is a patterned protection layer 200 a, asshown in FIG. 3B. The transparent conductive layer 102 a of the pixelelectrode pattern 110 is exposed, and the transparent conductive layer102 a of the bonding pads 114, 114 a is also exposed and allows anelectrical connection to the external circuit.

In the second embodiment of the invention, after the black materiallayer 202 is formed, then the protection layer 200 id formed on theblack material layer 202, as shown in FIG. 4A. At this moment, since theblack material layer 202 would cover over the surface of the secondmetal layer 122 a, the material of the black material layer 202preferably uses the black organic material or the black inorganicinsulating material.

Then, the fourth photomask process is likewise performed, to form apatterned photoresist layer 212 on the protection layer 200, and anetching process with the photoresist layer 212 as an etching mask isperformed, so as to pattern the protection layer 200 and the blackmaterial layer 202 to form the patterned protection layer 200 a and thepatterned black matrix pattern 202 a. Wherein, the patterned protectionlayer 200 a has the similar pattern to the black matrix pattern 202 a,as shown in FIG. 4B. In an embodiment, the patterned protection layer200 a and the black matrix pattern 202 a expose the transparentconductive layer 102 a of the pixel electrode pattern 110. In anotherembodiment, the patterned protection layer 200 a and the black matrixpattern 202 a further expose the transparent conductive layer 102 a ofthe bonding pads 114, 114 a and allow an electrical connection to theexternal circuit.

Third Embodiment

FIGS. 5A-5B are cross-sectional views, schematically illustrating thefabrication procedure for the pixel structure of the LCD, according tothe third preferred embodiment of the invention. In FIG. 5A, it is thesubsequent process from the previous processes in FIGS. 2A-2F. That is,after the third photomask process to form the second metal layer, aprotection layer 200, a black material layer 202 and another protectionlayer 204 are sequentially formed over the substrate 100. In anembodiment, the protection layer 200 and the protection layer 204include, for example, silicon oxide, silicon nitride, siliconoxynitride, or organic material. The black material layer 202 can be,for example, black organic material, black inorganic insulatingmaterial, or metallic material with capability to shield the light.

Then, a fourth photomask process is performed to form a patternedphotoresist layer 212 on the protection layer 204, and an etchingprocess is performed by using the photoresist layer 212 as the etchingmask, to pattern the protection layer 204, the black material layer 202and the protection layer 200. The patterned protection layer 204 a, theblack matrix pattern 202 a, and the patterned protection layer 200 a areformed, as shown in FIG. 5B. Wherein, the patterned protection layers204 a and 200 a have the similar pattern to the black matrix pattern 202a. In an embodiment, the patterned protection layer 204 a, the blackmatrix pattern 202 a, and the protection layer 200 a expose thetransparent conductive layer 102 a of the pixel electrode pattern 110.In another embodiment, further the patterned protection layer 204 a, theblack matrix pattern 202 a, and the protection layer 200 a expose thetransparent conductive layer 102 a of the bonding pads 114, 114 a andallow an electrical connection to the external circuit.

Fourth Embodiment

The pixel structure of the TFT LCD and the fabrication method of thefourth embodiment is a change from the foregoing three embodiments. Thechange is the step shown in FIG. 2A. After the transparent conductivelayer 102 is formed over the substrate 100, the metal layer 104 formedon the transparent conductive layer 102 is a multi-layer metallicstructure, for example, formed by two or three layers. The multi-layermetallic structure, for example, includes a selection from Cr, W, Ta,Ti, Mo, Al, or alloy thereof. In the embodiment, the first metal layer104 is, for example, a three-layer structure of Al/Cr/Al, a three-layerstructure of Mo/Al/Mo, or two-layer structure of Cr/Al. Particularly, ifthe transparent conductive layer 102 uses the ITO or IZO, then the filmlayer contacting with the transparent conductive layer 102 in themulti-layer metal layer 104 preferably uses Cr, W, Ta, Ti, Mo, Al, oralloy thereof.

Therefore, in the process of FIG. 2B, the metal layer for the gateelectrode pattern 108 defined within the preset region for forming theTFT T, the pixel electrode pattern 110 defined within the preset regionfor forming the pixel electrode P, and the scan line 150 (see FIG. 1)are formed from multiple metal layers. The metal portion of the lowerelectrode 112 and the bonding pads 114, 114 a is likewise formed frommultiple metal layers.

The subsequent processes, that are, the processes in FIG. 2C-FIG. 2D arethe same without further descriptions. In FIG. 2E, the second metallayer 122 over the substrate 100 is formed from multiple metal layers,such as two metal layers or three metal layers, and are composed oflayers of Cr, W, Ta, Ti, Mo, Al, and alloy thereof. Here, materials ofthe second metal layer 122 can be identical or different to the previousfirst metal layer 104.

Therefore, in processes of FIG. 2F, the metal layer portion of thesource electrode pattern 126, the drain electrode pattern 128, and thedata line 160 can be formed from multiple metal layers. Likewise, themetal portion of the upper electrode 129 of the pixel storage capacitorcan be formed from multiple metal layers.

For the subsequent processes, that are, the processes in FIG. 2G-FIG. 2Hand FIG. 3A-FIG. 3B for the first embodiment, the processes in FIG.4A-FIG. 4B for the second embodiment, the processes in FIG. 5A-FIG. 5Bfor the third embodiment are the same, and are not further described.

Pixel Structure

In the first embodiment, the pixel structure formed from four photomaskprocesses includes a TFT T, a pixel electrode P, and a black matrixpattern 202 a, as shown in FIG. 2H. Wherein, the TFT T is disposed on asurface of a substrate 100, and the TFT T includes a gate electrodepattern 108, a gate insulating layer 116 a disposed on the gateelectrode pattern 108, a semiconductor layer 118 a over the gateinsulating layer 116 a, and a source electrode pattern/drain electrodepattern 126/128 over the semiconductor layer 118 a. A pixel electrodepattern 110 of the pixel electrode P is disposed on a surface of thesubstrate 100, and the pixel electrode pattern 110 has electric contactwith the TFT T. In addition, the black matrix pattern 202 a covers overthe TFT T and exposes the pixel electrode pattern 110.

In an embodiment, the drain electrode pattern 128 of the TFT T covers aportion of the pixel electrode pattern 110. In another embodiment, thegate electrode pattern 108 includes a lower transparent conductive layer102 a and an upper metal layer 104 a. In an embodiment, the gateinsulating layer 116 a in the TFT T is just formed between thesemiconductor layer 118 a and the gate electrode pattern 108.

In the embodiment, the pixel structure further includes a storagecapacitor C, disposed on the substrate 100. The storage capacitor C isformed from a lower electrode 112, an upper electrode 129, that is, themetal layer 122 a above the lower electrode 112 and a dielectric layerbetween the two electrodes, such as the gate insulating layer with thesemiconductor layer 118 a. In an embodiment, the lower electrode 112 canbe formed from a lower transparent conductive layer 102 a and an uppermetal layer 104 a. In an embodiment, the upper electrode 129 covers aportion of the pixel electrode pattern 110.

In an embodiment, the pixel structure of the invention further includesbonding pads B and B′, disposed on two edges of the substrate 100. Thebonding pad pattern 114 of the bonding pad B is electrically coupledwith the scan line 150, and is formed from a lower transparentconductive layer 102 a and an upper metal layer 104 a. The upper metallayer 104 a exposes a portion of the lower transparent conductive layer102 a. The bonding pad pattern 114 a of the bonding pad B′ iselectrically coupled to the data line 160, and the structure is similarto that of the bonding pad B. The black matrix pattern 202 a exposes thelower transparent conductive layer 102 a of the bonding pad patterns114, 114 a, so as to allow an electric connection to the externalcircuit.

In the second embodiment, the pixel structure formed by four photomaskprocesses is similar to the structure in FIG. 2H. The difference is thatthe bottom side of the black matrix pattern 202 a is further formed witha protection layer 200 a, as shown in FIG. 3B. The pattern of theprotection layer 200 a is similar to the black matrix pattern 202 a.

In the second embodiment, another type of pixel structure is similar tothat in FIG. 2H, and the difference is that the upper surface of theblack matrix pattern 202 a further includes a patterned protection layer200 a, as shown in FIG. 4B. The patterned protection layer 200 a has thepattern similar to the black matrix pattern 202 a.

In the third embodiment, the pixel structure formed by four photomaskprocesses is similar to the structure in FIG. 2H. The difference is thatthe bottom side of the black matrix pattern 202 a is further formed witha patterned protection layer 200 a, and the upper surface of the blackmatrix pattern 202 a is further formed with another patterned protectionlayer 204 a, as shown in FIG. 5B. The patterned protection layer 200 aand the patterned protection layer 204 a has the similar patter to theblack matrix pattern 202 a.

LCD Panel

The LCD panel is shown in FIG. 6, including a TFT-array substrate 602, acolor-filter substrate 600, and a liquid crystal layer 604, wherein theforegoing TFT-array substrate 602 has several pixels, and each of thepixels of the TFT-array substrate 602 can have the structure in firstembodiment as shown in FIG. 2H, or the structure in second embodiment asshown in FIG. 3B, or another structure in second embodiment as shown inFIG. 4B, or a structure in third embodiment as shown in FIG. 5B.

The color-filter substrate 600 includes three color filter patters inred, green, and blue. The space between the three color filter patternsin red, green, and blue can be a white mesh clearance or a black matrix.In the invention, since the TFT-array substrate 602 has been formed withthe black matrix pattern, the color-filter substrate 600 can choose theone without formation of the black matrix. It is sure that the blackmatrix or other black matrix in different pattern can be chosen, such asthe black matrix in edge frame.

It will be apparent to those skilled in the art that variousmodifications and variations can be made to the structure of the presentinvention without departing from the scope or spirit of the invention.In view of the foregoing descriptions, it is intended that the presentinvention covers modifications and variations of this invention if theyfall within the scope of the following claims and their equivalents.

1. A pixel structure of liquid crystal display, comprising: a thin filmtransistor (TFT), disposed over a surface of a substrate, wherein theTFT includes a gate electrode pattern, a gate insulating layer disposedon the gate electrode pattern, a semiconductor layer over the gateinsulation layer, and a source electrode pattern with a drain electrodepattern formed over the semiconductor layer; a pixel electrode pattern,disposed over the surface of the substrate, wherein the drain electrodepattern of the TFT covers over a portion of the pixel electrode patternand electrically contact with the pixel electrode pattern; and a blackmatrix pattern, covering over the TFT and directly lying on parts of thepixel electrode pattern, and exposing the pixel electrode pattern. 2.The pixel structure of claim 1, further comprising a patternedprotection layer, covering over the black matrix pattern, and thepatterned protection layer has a pattern the same as the black matrixpattern.
 3. The pixel structure of claim 1, wherein the gate electrodepattern includes a lower transparent conductive layer and an upper metallayer.
 4. The pixel structure of claim 3, wherein the upper metal layeris a single metal layer, an alloy layer, or a metal multi-layer.
 5. Thepixel structure of claim 1, further comprising a storage capacitordisposed over the substrate, wherein the storage capacitor includes alower electrode, an upper electrode, and a dielectric layer, the lowerelectrode includes a lower transparent conductive layer and an uppermetal layer, and the upper electrode covers a portion of the pixelelectrode pattern.
 6. The pixel structure of claim 1, further comprisinga bonding pad pattern, disposed at two edges of the substrate, whereinthe bonding pad includes a lower transparent conductive layer and anupper metal layer, and the upper metal layer expose a portion of thelower transparent conductive layer.
 7. The pixel structure of claim 1,wherein each of the source electrode pattern and the drain electrodepattern are a single metal layer, an alloy layer, or a metalmulti-layer.
 8. A liquid crystal display (LCD) panel, comprising: a thinfilm transistor (TFT)-array substrate, a color-filter substrate, and aliquid crystal layer, wherein the TFT-array substrate has a plurality ofpixels, and each of the pixels comprises: a TFT, comprising a gateelectrode pattern, a gate insulating layer disposed on the gateelectrode pattern, a semiconductor layer covering over the gateinsulating layer, and a source electrode pattern with a drain electrodepattern fanned on the semiconductor layer; a pixel electrode pattern,disposed over the ITT-array substrate, and the drain electrode patternof the TFT covers over a portion of the pixel electrode pattern andelectrically contact with the pixel electrode pattern; and a blackmatrix pattern, covering the ITT and directly lying on parts of thepixel electrode pattern, and exposing the pixel electrode pattern. 9.The LCD panel of claim 8, further comprising a patterned protectionlayer, covering over the black matrix pattern, and the patternedprotection layer has a pattern the same as the black matrix pattern.